Inclusive fitness and differential productivity across the life course determine intergenerational transfers in a small-scale human society

Transfers of resources between generations are an essential element in current models of human life-history evolution accounting for prolonged development, extended lifespan and menopause. Integrating these models with Hamilton's theory of inclusive fitness, we predict that the interaction of b...

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Published in:Proceedings of the Royal Society. B, Biological sciences Biological sciences, 2015-03, Vol.282 (1803), p.20142808-20142808
Main Authors: Hooper, Paul L., Gurven, Michael, Winking, Jeffrey, Kaplan, Hillard S.
Format: Article
Language:English
Subjects:
Adolescent
Adult
Age Factors
Aged
Agriculture
Biological Evolution
Bolivia
Child
Child, Preschool
Cooperative Behavior
Efficiency
Family
Family Relations
Feeding Behavior
Female
Food Sharing
Genetic Fitness
Grandparental Investment
Human Life History
Humans
Inclusive Fitness
Indians, South American
Infant
Intergenerational Transfers
Male
Middle Aged
Parental Investment
Sex Factors
Social Behavior
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Summary:Transfers of resources between generations are an essential element in current models of human life-history evolution accounting for prolonged development, extended lifespan and menopause. Integrating these models with Hamilton's theory of inclusive fitness, we predict that the interaction of biological kinship with the age-schedule of resource production should be a key driver of intergenerational transfers. In the empirical case of Tsimane’ forager–horticulturalists in Bolivian Amazonia, we provide a detailed characterization of net transfers of food according to age, sex, kinship and the net need of donors and recipients. We show that parents, grandparents and siblings provide significant net downward transfers of food across generations. We demonstrate that the extent of provisioning responds facultatively to variation in the productivity and demographic composition of families, as predicted by the theory. We hypothesize that the motivation to provide these critical transfers is a fundamental force that binds together human nuclear and extended families. The ubiquity of three-generational families in human societies may thus be a direct reflection of fundamental evolutionary constraints on an organism's life-history and social organization.
ISSN:0962-8452
1471-2954
DOI:10.1098/rspb.2014.2808